This relates generally to bit alterable memories.
A bit alterable memory is a memory that can be altered by writing at the bit level. For example, flash memories generally are written in bulk across a number of cells at the same time. Bit alterable memories, such as lone-pair semiconductor or phase change memories, dynamic random access memories, polymer memories, ferroelectric random access memories, and magnetic random access memories can be written one bit at a time.
Phase change memory devices use phase change materials, i.e., materials that may be electrically switched between a generally amorphous and a generally crystalline state, for electronic memory application. One type of memory element utilizes a phase change material that may be, in one application, electrically switched between a structural state of generally amorphous and generally crystalline local order or between different detectable states of local order across the entire spectrum between completely amorphous and completely crystalline states. The state of the phase change materials is also non-volatile in that, when set in either a crystalline, semi-crystalline, amorphous, or semi-amorphous state representing a resistance value, that value is retained until changed by another programming event, as that value represents a phase or physical state of the material (e.g., crystalline or amorphous). The state is unaffected by removing electrical power.